Laser Arrangement having a Laser Diode Apparatus and Method for Stabilizing Operating Temperature Distribution of a Laser Diode Apparatus

ABSTRACT

A laser arrangement has at least one laser diode apparatus with a side surface which laterally limits the laser diode apparatus. The laser arrangement has a plurality of active regions arranged laterally side by side and configured to generate radiation. The laser diode apparatus is arranged on a mount. The distance between the side surface and an edge which laterally limits the mount on the part of the side surface is shorter than the distance between the side surface and the active region closest to the side surface. Additionally or alternatively, the distance between the side surface and the edge is shorter than one of the distances between two adjacent active regions of the laser diode apparatus.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a division of co-pending U.S. patentapplication Ser. No. 11/541,131 filed Sep. 28, 2006, now allowed,claiming priority to German Patent Application No. 10 2005 046 785.5filed Sep. 29, 2005, the entire disclosure content of which is herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a laser arrangement having a laserdiode apparatus. The invention also relates to a method for stabilizingoperating temperature distribution of a laser diode apparatus.

BACKGROUND OF THE INVENTION

The peak wavelength of the radiation which is produced in a singleactive region of a laser diode chip frequently has a significanttemperature response, that is to say it varies with the operatingtemperature of the active region. In the case of laser diodes based ongallium arsenide, the peak wavelength typically changes by approximately0.3 nm/K. The operating temperature is generally governed primarily bythe loss heat which occurs during radiation production, with thequantity of loss heat depending on the conversion efficiency ofelectrical power to radiation power in the active region of the laserdiode, in the case of electrically pumped lasers.

In the case of laser diode arrangements having a plurality of activeregions, different active regions may be at different operatingtemperatures. This can lead to an increase in the differences betweenthe peak wavelengths of the radiation produced in the respective activeregions, or may be a reason for the occurrence of such differences.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a laser arrangementhaving a laser diode apparatus, in which case the laser diode apparatusand the laser arrangement can be operated in a simplified form, withless fluctuation between the operating temperatures of different activeregions.

This and other objects are attained in accordance with one aspect of thepresent invention directed to a laser diode apparatus having a pluralityof active regions which are arranged laterally side by side and aresuitable for radiation production, with a lateral dimension of theactive regions being varied in the lateral direction, and/or thedistance between adjacent active regions being varied in the lateraldirection.

The active regions are expediently designed to produce radiation duringoperation of the laser diode apparatus.

The laser diode apparatus preferably has a lateral main direction ofextent. The active regions are particularly preferably arranged in a rowside by side along the main direction of extent.

Two active regions between which a further active region is arranged arenot to be regarded as adjacent active regions in the above sense.

The radiation-producing active area of the respective active region canbe varied by variation of the lateral dimensions of the active regions.This makes it possible to deliberately influence the quantity of lossheat which occurs in the respective active region. The larger theradiation-producing area, the greater the quantity of loss heat which isproduced in the respective active region generally is and,correspondingly, also the operating temperature of the respective activeregion. The operating temperature distribution over the active regionsof the laser diode apparatus can accordingly be influenced deliberatelyby local variation of the lateral dimension of the active regions, andin particular by variation of the active area of the active regions.

A corresponding situation applies to the variation of the distancebetween adjacent active regions. The operating temperatures of twoadjacent active regions are generally increased as the distance betweenthese active regions is decreased, because the loss heat is thenproduced in a locally more concentrated form.

A predetermined distribution of the operating temperature of the variousactive regions of the laser diode apparatus in the lateral direction canbe achieved in a simplified manner by suitable variations of thedistance between adjacent active regions and/or the lateral dimension ofthe active regions of the laser diode apparatus. The operatingtemperature distribution is preferably formed by appropriate arrangementand/or configuration of the active regions in such a manner as toproduce a predetermined operating temperature distribution.

The active regions are preferably arranged and/or configured in such amanner that, during operation of the laser diode apparatus, this resultsin an operating temperature distribution over different active regionsalong a lateral main extent direction of the laser diode apparatus whichis more homogeneous than in the case of a further laser diode apparatuswhich, by way of example, has active regions arranged equidistantly,with each of the active regions having the same lateral dimension. Thisallows for a laser diode apparatus to be designed with a stabilizedoperating temperature.

In particular, the active regions can be arranged and/or configured suchthat the operating temperature of the active regions is the same atcorresponding locations selected in the same way in the respectiveactive region.

For this purpose, by way of example, a reference laser diode apparatuscan first of all be manufactured which has active regions arrangedequidistantly and with the same lateral dimensions. The operatingtemperature distribution of the reference laser diode apparatus can thenbe measured. In zones of the reference laser diode apparatus in whichthe active regions are at a comparatively low operating temperature, thelaserdiode apparatus which is then to be produced and whose operatingtemperature is stabilized is designed to have active regions whoselateral dimension is greater than that of the reference laser diodeapparatus, and/or to have active regions whose separation is less thanthat of the active regions of the reference laser diode apparatus. Incomparison to the active regions with a low operating temperature in thereference laser diode apparatus, the quantity of loss heat in this zoneof the laser diode apparatus is deliberately increased in the laserdiode apparatus whose operating temperature is stabilized. This thenresults in a correspondingly increased operating temperature in therespective active regions of the laser diode apparatus whose operatingtemperature is stabilized.

In consequence, the peak wavelengths of the laser radiation produced bythe active regions of the laser diode apparatus can be stabilized. Thisis particularly advantageous in the case of active regions which aredesigned to be identical, in particular to produce radiation at the samepeak wavelengths and at the same operating temperature. The emissionspectrum of the laser diode apparatus can thus be narrowed, owing to thestabilization of the peak wavelengths, in comparison to an emissionspectrum from a laser diode apparatus which has an inhomogeneousoperating temperature distribution over different active regions. Thisis particularly advantageous for applications for which a narrowbandemission spectrum is expedient.

A narrowband emission spectrum is advantageous, for example, in the caseof pump applications, in which a laser diode apparatus is used foroptical pumping of a further radiation source, such as a laser.

A laser to be pumped in this way may be in the form of a solid-statelaser, for example a solid-state disk laser or solid-state rod laser, afiber laser or a semiconductor laser, for example a semiconductor laserwith an external resonator and/or a semiconductor disk laser. Lasers tobe pumped optically generally have a comparatively narrowband absorptionspectrum in the medium of the laser which is to be pumped. Broadening ofthe emission characteristic of the laser diode apparatus thus reducesthe pumping efficiency of the laser diode arrangement which is used asthe pump laser. Such a broadening of the emission spectrum can becounteracted by the design of the laser diode apparatus according to theinvention.

In principle, the operating temperature distribution could also behomogenized by increasing the efficiency of the active regions forradiation production, with a corresponding reduction in the productionof loss heat. However, this is comparatively complex and costly incomparison to the variation of the lateral dimension of the activeregions, or of the distance between adjacent active regions.

In one preferred refinement, the laser diode apparatus has at least oneside surface which laterally limits the laser diode apparatus. In theregion of the side surface, the operating temperature of the activeregions which are arranged in this region of the laser diode apparatus,for example because of better heat dissipation or because less loss heatis produced, is often less than in regions which are further away fromthe side surface.

In one preferred refinement of the laser diode apparatus, the lateraldimension of one active region is therefore greater than the lateraldimension of another active region, with this active region beingadjacent to the first active region, and being further away from theside surface than the first active region.

Alternatively or additionally, the distance between the active regionsof one pair with two adjacent active regions is preferably shorter thanthe distance between the active regions of another pair with twoadjacent active regions, which is further away from the side surfacethan the first pair. In this case, at least one active region of theother pair is further away from the side surface than each active regionof the first pair. If applicable, both pairs may have one common activeregion. An arrangement of this kind allows for increased loss heat to beproduced in a simplified manner in the region of the side surface, sothat the operating temperature can be increased deliberately in thoseactive regions of the laser diode apparatus which are arranged close tothe side surface.

In a further preferred refinement, the lateral dimension of the activeregions decreases, in particular the respective lateral dimension, asthe distance between the active regions and the side surface increases,in particular stepwise.

Alternatively or additionally, the distance, in particular therespective distance, between adjacent active regions preferablyincreases as the distance between the active regions and the sidesurface increases, in particular in steps. The loss heat which isproduced in active regions that are comparatively far away from the sidesurface can be reduced in a simplified manner by this arrangement, aswell as the operating temperature of these active regions. This makes itpossible to achieve a homogeneous operating temperature distribution inthe lateral direction over the active regions of the laser diodeapparatus, in a simplified manner.

The laser diode apparatus preferably has four or more, particularpreferably ten or more, active regions. Fluctuations in the operatingtemperature distribution between individual active regions occur to anincreased extent in a laser diode apparatus such as this, because of thelarge number of active regions. Thus, in this case, homogenization ofthe operating temperature distribution has a particularly pronouncedeffect.

In one preferred refinement, the active regions of the laser diodeapparatus are arranged on a common substrate. This allows the laserdiode apparatus to be designed to be particularly compact, with thesubstrate preferably mechanically stabilizing the active regions. Since,when the laser diode apparatus is designed to be compact in this way,inhomogeneities in the operating temperature distribution of the activeregions are particularly strongly pronounced. Thus, homogenization ofthe operating temperature is particularly advantageous in this case.

That side surface which limits the laser diode apparatus in the lateraldirection is preferably formed by the substrate, at least in places.

In order to prevent lateral widening of the heat flow and reduction inthe operating temperature associated therewith in active regions whichare arranged comparatively close to that region of the side surfacewhich is formed by the substrate, that active region which is closest tothe side surface, in particular that active region which is closest tothe region of the side surface formed by the substrate, is preferablyarranged at a distance from the side surface which is shorter than orequal to one of the distances between two adjacent active regions.

In a further preferred refinement, the distance between that activeregion which is closest to the side surface and the side surface isshorter than the distance between this active region and an activeregion which is adjacent to this active region and is preferablyarranged on that side of the active region closest to the side surfacefacing away from that side surface.

Furthermore, the distance between that region of the side surface whichis formed by the substrate and the closest active region is preferablyshorter than the shortest of the distances between the active regions.If the distance between the active regions in the laser diode apparatusvaries, the operating temperatures of the active regions can in this waybe matched to one another in a simplified manner. If applicable, oneactive region may adjoin the side surface, and/or end flush with theside surface.

In a further preferred refinement, the active regions are arrangedaxially symmetrically with respect to an axis of symmetry of the laserdiode apparatus. The axis of symmetry is preferably arrangedperpendicularly to the lateral direction of main extent of the laserdiode apparatus, or runs essentially parallel to one surface of thesubstrate, on which the active regions are arranged. A symmetricalarrangement of this kind makes it easier to achieve a homogeneous,symmetrical operating temperature distribution over the active regionsof the laser diode apparatus.

In a first advantageous development, two active regions of the laserdiode apparatus, in particular all of the active regions of the laserdiode apparatus, are each associated with discrete laser diode chips.These chips are expediently mounted on the substrate. The substrate isin this case preferably formed by a heat sink or a submount. Thesubmount is preferably in the form of a heat spreader. The heat spreaderis particularly preferably arranged between the laser diode chips and anadditionally provided heat sink.

The submount is preferably matched to the thermal coefficient ofexpansion of the laser diode chips, which are preferably designed to beidentical. In the case of discrete laser diode chips, the operatingtemperature can be stabilized in a particularly simple manner byappropriate choice of the distances between the individual chips whenthe chips are being mounted on the substrate. In the case of discretelaser diode chips, the active regions and in particular the individuallaser diode chips are separated from one another by a free space. Thelaser diode chips are preferably implemented as edge-emitting lasers.

In a further advantageous development, two active regions are associatedwith one common laser diode chip, in particular a laser diode bar. Inthis case, the substrate is preferably formed by the growth substratefor the active regions of the laser diode chip, or is formed from thegrowth substrate. The laser diode apparatus is preferably implemented asa laser diode chip.

Two active regions of the laser diode chip, preferably all of the activeregions of the chip, may in this case be formed by regions of acontinuous active layer, which regions are provided with currentdiscretely from one another, and which layer is preferably part of asemiconductor layer sequence of the laser diode chip. Alternatively oradditionally, two active regions of the laser diode chip can beseparated from one another by a free space. In particular, the activeregions may be formed in semiconductor bodies which are separated fromone another by a free space.

Active regions of the laser diode chip are preferably either in the formof regions of a continuous active layer which are provided with currentdiscretely from one to the other, or are separated from one another by afree space.

In the former case, the operating temperature distribution can behomogenized by a suitable configuration of electrical contacts, forexample contact metallizations, for current injection into therespective active region. The contacts may be arranged striplike, and inparticular side by side on the active layer. Furthermore, the contactwhich is associated with the respective active region preferably coversthis active region at least partially, and particularly preferablycompletely.

The features described further above and in the following text for thedistances between and/or lateral dimensions of active regions canaccordingly be used in a laser diode chip in which the correspondingactive regions are formed by regions of a continuous active layerthrough which regions current flows discretely from one another, for thecorresponding embodiment of the contacts for the discrete currentinjection into the active layer. Corresponding homogenization of theoperating temperature distribution over the active regions canaccordingly be achieved by the configuration of the contactgeometry—variation of the width and/or of the distances between thecontacts in the lateral direction—for the current flow for discreteactive regions.

If the laser diode chip is designed with active regions which areseparated from one another by a free space, for example in discretesemiconductor bodies, a semiconductor layer sequence with an activelayer can be structured by means of a suitable mask in such a mannerthat the lateral dimensions of adjacent active regions and/or thedistances between adjacent active regions—for example between discretesubregions of the active layer which is continuous before thestructuring process—vary over the chip.

In the case of a laser diode bar, the active regions, in particular asemiconductor layer structure which comprises the respective activeregion, are preferably configured for an edge-emitting laser structure.Edge-emitting laser structures emit radiation essentially parallel tothe active region. Furthermore, the active regions are preferablydesigned to be identical, that is to say in order to produce radiationof the same peak wavelength at the same operating temperature. Theactive regions, in particular the active layer, may for example be grownepitaxially on the substrate, which is then used as a growth substrate.

A laser diode bar is often used to produce a high radiation power, andis accordingly operated with a high electrical power. Because of thehigh electrical power consumption, the peak wavelengths of the radiationproduced in different active regions may differ from one anotherconsiderably if the operating temperature distribution over the activeregions of a laser diode bar is not stabilized adequately. Differingpeak wavelengths can be avoided within the scope of the invention.

A laser arrangement according to an embodiment of the invention has atleast one laser diode apparatus which has a side surface which laterallylimits the laser diode apparatus, and has a plurality of active regionswhich are arranged laterally side by side and are suitable for radiationproduction, with the laser diode apparatus being arranged on a mount,and the distance between the side surface and an edge which laterallylimits the mount on the part of the side surface is shorter than thedistance between the active region closest to the side surface and theside surface, and/or the distance between the side surface and the edgeis shorter than one of the distances between two adjacent active regionsof the laser diode apparatus.

The active regions are expediently designed to produce radiation duringoperation of the laser diode apparatus.

The mount for the laser diode apparatus is thus matched to the size ofthe laser diode apparatus. The mount is preferably matched to the laserdiode apparatus in such a manner that the lateral widening of the heatflow, particularly in the mount, is reduced. In the same way as by themeasures described further above, this also allows for influencing theoperating temperature distribution over the active regions of the laserdiode apparatus. Loss heat which is dissipated from the laser diodeapparatus into the mount in the region of the side surface of theapparatus is subject to only a relatively small amount of lateralwidening of the heat flow in the edge-region of the mount because of theside surface and the mount edge being arranged comparatively close toone another. The operating temperature of the active regions which arelocated comparatively close to the side surface is thus not considerablyless than the operating temperature of active regions that are furtheraway from the side surface. This is because of the only moderatewidening of the heat flow in the mount. The operating temperatures ofthe active regions can be matched to one another in a simplified mannerby an arrangement of this kind of the laser diode apparatus relative tothe mount. As has already been described further above, this makes itpossible to stabilize the peak wavelengths of the radiation produced inthe various active regions.

The mount preferably limits the laser arrangement at least in places inthe lateral direction. An arrangement of the side surface as close aspossible to the edge of the mount has been found to be particularlyadvantageous in order to reduce or completely avoid the widening of theheat flow in the edge region of the mount.

The distance of the side surface from the edge is preferably shorterthan the shortest of the distances between the active regions of thelaser diode apparatus. It is particularly preferable for the sidesurface, in particular on its side facing the mount, to end flush withthe mount. This makes it possible to essentially completely avoidwidening of the heat flow in the lateral direction in the mount.

Furthermore, the mount is preferably in the form of a heat sink or, inparticular, a submount. Loss heat occurring in the active regions canthus be reliably dissipated away from the active regions.

If applicable, the submount may be arranged between the laser diodeapparatus and another mount for the laser arrangement, for example aheat sink. Such as compared to the heat sink, the submount is preferablybetter matched to the thermal coefficient of expansion of an element ofthe laser diode apparatus on the side facing the submount. In particularwith respect to the thermal coefficient of expansion, the mount can thusbe matched to the thermal coefficient of expansion of the laser diodeapparatus with, for example, a discrepancy of 5% or less. This makes itpossible to reduce the risk of thermally caused damage to the laserdiode apparatus.

A submount containing copper-tungsten (CuWo) is particularly suitablefor matching of the thermal coefficient of expansion, and for goodthermal conductivity. The ratio of copper to tungsten can be used tovary the thermal coefficient of expansion of a heat spreader such asthis and to match it to the thermal coefficient of expansion of thelaser diode apparatus, in particular to that of the substrate of thelaser diode apparatus or that of a semiconductor material arranged onthe part of the heat spreader. Particularly good thermal matching can beachieved for a laser diode chip based on gallium arsenide, for examplewith a (growth) substrate containing gallium arsenide, and/or an activeregion based on gallium arsenide.

A copper heat sink is particularly suitable for use as a heat sink.

In a further preferred refinement, the substrate is arranged on the sideof the active regions facing away from the mount. The heat dissipationfrom the active regions to the mount can be improved in this way sincethe heat need not be passed through the substrate. The substrate is inthis case expediently formed by the growth substrate. The risk of damageto the laser diode apparatus as a result of temperatures that are raisedbecause of a heat jam can thus be reduced. However, because of thebetter heat dissipation, differences in the operating temperatures ofthe active regions are increased in a particularly pronounced form whenthe substrate is arranged in this way. In this case, it is particularlyadvantageous to stabilize the operating temperature by variation of thelateral dimensions and/or the distances between the active regions,and/or to appropriately match the dimensions of the laser diodeapparatus to the mount.

In a further preferred refinement, the contacts for the active regionsare arranged between the mount and the active layer.

The laser diode apparatus of the laser arrangement is preferablyimplemented as a laser diode apparatus according to an embodiment of theinvention as described above. The operating temperature distribution canthus be influenced to a greater extent and in a simplified manner.Features which have been described above and those which will bedescribed in the following text in conjunction with the laser diodeapparatus according to embodiments of the invention can thus also applyto the laser arrangement according to embodiments of the invention, andvice versa.

The laser arrangement and the laser diode apparatus can be designed in asimplified form, owing to the capability to influence the operatingtemperature distribution, with the operating temperature distributionrunning in the same way in the lateral direction in the respectiveactive regions. This effect is particularly pronounced in the case ofactive regions which are designed to be identical and which the laserdiode apparatus preferably has. These should nominally emit radiation atthe same peak wavelength, although this wavelength may vary owing todifferences in the operating temperature. This fluctuation can bereduced or completely overcome by the invention. A laser diode apparatuswhose operating temperature is stabilized in this way, or acorresponding laser arrangement, is accordingly particularly suitablefor a pump application, in which a radiation source to be pumped ispumped optically by means of absorption of the radiation produced by thelaser diode apparatus.

An optically pumped laser according to embodiments of the invention ispumped by means of a laser diode apparatus according to embodiments ofthe invention, or by means of a laser arrangement according toembodiments of the invention.

Owing to the stable peak wavelength, these lasers are particularlysuitable for use as pump lasers for efficient pumping.

The laser to be pumped is preferably in the form of a solid-state laser,in particular a solid-state disk laser or a solid-state rod laser, afiber laser or a semiconductor laser, in particular a semiconductor disklaser.

The pump radiation source is particularly suitable for pumping asemiconductor laser, in particular a surface-emitting semiconductorlaser, which is intended for operation with an external resonator. Forexample, the semiconductor laser is in the form of a VECSEL (VerticalExternal Cavity Surface Emitting Laser) and/or a disk laser.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1F show exemplary embodiments of a laser arrangement on thebasis of a schematic section view in FIG. 1A and a schematic plan viewin FIG. 1B, a further laser arrangement on the basis of correspondingviews in FIGS. 1C and 1D, and a further laser arrangement in FIG. 1E,and also the quantitative operating temperature profile of a laserarrangement in FIG. 1F;

FIGS. 2A-2B show one exemplary embodiment of a laser arrangement on thebasis of a schematic plan view in FIG. 2A and a schematic section viewin FIG. 2B;

FIGS. 3A-3B show two exemplary embodiments of a laser diode chip on thebasis of schematic plan views;

FIGS. 4A-4B show two exemplary embodiments of a laser arrangement on thebasis of schematic section views;

FIGS. 5A-5B show two further exemplary embodiments of a laser diode chipon the basis of schematic plan views;

FIG. 6 shows a schematic view of one exemplary embodiment of anoptically pumped semiconductor laser; and

FIG. 7 shows a schematic view of one exemplary embodiment of anoptically pumped laser.

DETAILED DESCRIPTION OF THE DRAWINGS

Identical elements, elements of the same kind and identically actingelements are provided with the same reference symbols in the Figures.

A laser arrangement 1 is shown as a schematic section view in FIG. 1Aand a schematic plan view onto the laser arrangement in FIG. 1B.

The laser arrangement 1 has a laser diode chip 2, which comprises aplurality of active regions 4 a, 4 b, 4 c, 4 d, . . . , 4 n which arearranged side by side on a common substrate 3 along a lateral directionof main extent R of the laser diode chip and are suitable for radiationproduction. The laser diode chip 2 preferably comprises ten or moreactive regions, for example twelve active regions.

As is shown in the illustration in FIGS. 1A and 1B, an active region isin each case formed in a semiconductor body 5 a, 5 b, 5 c, 5 d, . . . 5n. The semiconductor bodies 5 a . . . 5 n are in the form of discretesemiconductor structures, which are arranged spatially separated fromone another on the substrate 3. The semiconductor bodies 5 a . . . 5 nare arranged in particular at equal intervals on the substrate 3 andhave the same lateral dimensions, that is to say the same widths, alongthe lateral direction of main extent. A length dimension of thesemiconductor bodies, that is to say their length, taken at right anglesto the lateral main extent direction is preferably greater than thelateral dimension, and is particularly preferably constant. Furthermore,the active regions preferably have the same area content, that is to saythe same active area.

The laser diode chip 2 in the laser arrangement 1 is arranged on a mount6, with the substrate 3 preferably being arranged between the activeregions 4 a . . . 4 n and the mount. In the lateral direction, the mount6 is laterally bounded by a first edge surface 7 and a second edgesurface 8, with the second edge surface 8 being arranged opposite of thefirst edge surface 7. The edge surfaces 7, 8 at the same time also boundthe laser arrangement 1 in the lateral direction. The laser diode chip 2is bounded in the lateral direction by a first side surface 9 and asecond side surface 10. These are formed by the substrate 3. The secondside surface 10 is arranged opposite of the first side surface 9.Furthermore, the edge surfaces 7, 8 are arranged at a distance from theside surfaces 9, 10. In addition, the active regions are arranged at adistance from the side surfaces 9 and 10, such that the laserarrangement has a structure which broadens laterally in the form ofsteps, starting from the active regions.

The semiconductor bodies 5 a . . . 5 n are formed on the basis ofedge-emitting laser structures. A resonator for a laser structure ofthis kind can be formed by means of a first reflector surface 11 and asecond reflector surface 12, which the respective semiconductor bodies 5a . . . 5 n may have or which may be formed on the respectivesemiconductor body. One surface of the respective semiconductor bodypreferably forms the respective reflector surface. The first reflectorsurface 11 is preferably less reflective than the second reflectorsurface 12, so that, during operation of the laser diode chip 2, aradiation field can be formed in the resonator of the respectivesemiconductor body, can be amplified therein, and can be output from theresonator as laser radiation 13 via the reflector surface 11 which isused as the output surface.

The semiconductor bodies 5 a . . . 5 n are preferably monolithicallyintegrated. The semiconductor bodies may be epitaxially grown on thesubstrate 3. The semiconductor bodies are preferably based on galliumarsenide. A gallium-arsenide substrate is in this case particularlysuitable for use as the substrate, and in particular also as a growthsubstrate for epitaxial growth of the semiconductor bodies.

Furthermore, the active regions are preferably formed to be identical,in particular for emission of laser radiation at the same peakwavelength at the same operating temperature. Active regions which havea single-quantum-well or multiple-quantum-well structure areparticularly suitable for efficient radiation production. The expressionquantum-well structure does not include any details about thedimensions. It thus covers, inter alia, quantum troughs, quantum wires,quantum points and any combination of these structures.

Laser diode chips based on (In,AI)GaAs are particularly suitable forradiation production in the infrared spectral range.

During operation of the laser diode chips 2, e.g. in quasi-continuouslong-pulse operation (qcw: quasi-continuous wave) or continuous waveoperation (cw: continuous wave), radiation is produced in the activeregions. The quantity of loss heat in this case generated can beconsiderably high. In the case of high-power laser diode chips—forexample with an output power of a chip with one active region of ≧1 Wand for a chip with a plurality of active regions of ≧10 W—thecorresponding quantity of loss heat is particularly high. In order toavoid a significant increase in the risk of heat-caused damage to theactive regions, the mount 6 is preferably implemented as a heat sink forheat dissipation from the laser diode chip. For this purpose, the mount6 contains for example a metal, e.g. copper, or an alloy, e.g.copper-tungsten, with a thermal conductivity being advantageously high.The heat can be dissipated from the active regions via the substrate 3into the mount 6.

The laser arrangement 1 with the mount 6 can be arranged on a connectioncarrier (not illustrated), for example a circuit board, and electricallycontact connected thereon. The electrical contacts for the laserarrangement have not been illustrated explicitly, for clarity reasons.The mount may serve as a submount for the laser diode chip, and isarranged between the laser diode chip and the connection carrier and/orbetween the chip and an additional heat sink, for this purpose.

In those active regions which are adjacent to the side surfaces 9 and10, or are arranged close to the respective side surfaces, for examplethe active regions 4 a and 4 n, the loss heat which occurs can beconducted within the substrate in the lateral direction to therespective side surface of the substrate. Heat which passes from thesubstrate 3 in the vertical direction into the mount 6 can be passedlaterally in the direction of the edge surfaces 9 and 10 within themount. The heat flow can thus be widened in the lateral direction withinthe substrate or within the mount. This is illustrated schematically inFIG. 1A by the heat flow lines 14 and 15, which widen in the lateraldirection. The quantity of the loss heat which is produced in the edgeregions of the laser diode chip, that is to say those regions close tothe side surfaces, is less than in the middle, central region of thelaser diode chip 2. Owing to the widening of the heat flow and thecomparatively large area which is available for heat dissipation to theside of the side surface, this heat is dissipated from the activeregions to an increased extent.

In consequence, an operating temperature gradient is formed in theactive regions in the lateral direction. The operating temperaturesT_(a), T_(b), T_(c), T_(d), . . . and T_(n) of the active regions 4 a, 4b, 4 c, 4 d, . . . and 4 n, respectively, thus increase as the distancefrom the side surfaces 9 and 10 increases in the lateral direction. Thefurther the active regions are away from the side surfaces 9 and 10 orthe edge surfaces 7 and 8, the less the lateral widening of the heatflow in the edge region influences the operating temperature of therespective active regions. Rather, in zones of the laser diode chipwhich are relatively far away from the side surfaces, the heat can bedissipated from the active regions essentially without broadening of theheat flow, and directly in the vertical direction.

The operating temperatures of the active regions are preferablydetermined at corresponding locations in the respective active regionalong the lateral main extent direction. For example, the operatingtemperature of an active region is determined in the center of thisactive region on the side of the first reflector surface 11.

Also, when individual chips are arranged alongside one another, that isto say a plurality of laser diode chips which have been producedseparately from one another but are mounted on a common chip mount, andassuming that the chips are arranged at equal distances, it is alsopossible for a gradient to occur in the operating temperaturedistribution as a result of the lateral widening of the heat flow (notexplicitly illustrated). In this case, in the illustration in FIG. 1,the semiconductor bodies would correspond to individual laser diodechips, the substrate 3 to the chip mount which, for example, is in theform of a heat spreader or a submount, and the mount 6 to a heat sink ora connection carrier for the chips mounted onto the chip mount. Formatching the thermal coefficients of expansion to the ones of theindividual laser diode chips, a copper-tungsten submount and a copperheat sink are particularly suitable. The individual laser diode chipsare preferably designed to produce radiation of the same peakwavelength.

The laser arrangement 1 illustrated schematically in FIGS. 1C and 1Dcorresponds essentially to the laser arrangement illustrated in FIGS. 1Aand 1B. In contrast to this, the laser diode chip 2 has a semiconductorlayer structure 500 with a continuous active layer 400, which isarranged on the substrate 3. The semiconductor layer structure 500preferably ends flush with the side surfaces 9, 10 of the substrate 3.In contrast to FIGS. 1A and 1B, the active regions 4 a . . . 4 n of thelaser diode chip 2 are formed by regions of the active layer 400 throughwhich regions current flows discretely from one to the other duringoperation of the semiconductor chip. The reflector surfaces 11, 12 arealso formed by a continuous surface. The active regions 4 a . . . 4 nare each covered by an electrical contact, in particular a contactmetallization. One and only one contact is preferably associated witheach active region.

The shape and the arrangement of the discrete contacts 50 a . . . 50 ncorrespond to the respective semiconductor bodies 5 a . . . 5 n as shownin FIGS. 1A and 1B. In particular, the contacts 50 a . . . 50 n arearranged at equal distances from one another in the lateral direction onthe semiconductor layer structure 500. In consequence, the activeregions 4 a . . . 4 n which produce radiation during operation of thelaser diode chip 2 are likewise arranged at equal distances from oneanother.

The contacts are preferably in the form of contact strips which, inparticular, run parallel to one another. Furthermore, the contacts havethe same widths.

In a corresponding manner, the operating temperature distribution in thelateral direction in the laser diode chip 2 illustrated in FIGS. 1C and1D can likewise run inhomogeneously, in the same way as in the case ofthe chip shown in FIGS. 1A and 1B. The continuous semiconductor layerstructure which, in addition to the active layer 400, preferably alsocontains a plurality of additional semiconductor layers, can constrainthe heat dissipation from the active regions even further. Thefluctuations in the operating temperature may be increased even furtherin comparison to those active regions which are separated from oneanother by a free space.

The laser diode chip 2 can be fixed on the mount 6 by means of apreferably electrically and/or thermally conductive connection layer(not illustrated) and, in particular, can be electrically and/orthermally conductively connected to the mount 6. The connection layer ispreferably arranged between the laser diode chip and the mount 6. Theconnection layer may be in the form of a solder layer, in particular anindium solder layer.

In order to arrange the active regions 4 a . . . 4 n closer to the mountfor improved heat dissipation, the active regions can be arrangedbetween the mount 6 and the substrate 3. In particular, the contacts 50a . . . 50 n serving for discrete current impression into the activelayer can be arranged between the semiconductor layer structure 500 andthe mount 6 (FIG. 1E). The heat dissipation from the active regions canbe improved by arranging the substrate 3 on that side of the activeregions which faces away from the mount. The risk of damage to the laserdiode chip caused by excessive temperatures during operation of thelaser arrangement 1 is thus reduced. Since a refinement such as thisimproves the thermal link to the mount 6, lateral widening of the heatflow in the mount can be observed to an increased extent. This furtherincreases the fluctuations in the peak wavelengths.

The laser diode chips illustrated in FIGS. 1A to 1E are preferably inthe form of laser diode bars.

FIG. 1F shows the operating temperature profile quantitatively, that isto say the change in the operating temperature ΔT in DC along thedistance x in μm along the lateral main extent direction, from thecenter of the laser diode chip in the direction of the side surface 9 ofthe substrate 3, for a laser arrangement similar to the arrangementsshown in FIGS. 1A, 1B as well as IC, 1D and 1E for different fillingfactors F of the substrate with active regions. The decrease in theoperating temperatures in the direction of the side surface can clearlybe seen.

Since the peak wavelength of the radiation produced in the respectiveactive region depends on its operating temperature, this operatingtemperature gradient leads to different peak wavelengths of theradiation produced in the respective active regions. The emissionspectrum of the laser diode chip 2 is thus broadened because the peakwavelength is dependent on the temperature. This may be undesirable forapplications of the laser arrangement such as the pumping of asolid-state laser, which in general has a narrow absorption spectrum.The peak wavelength may vary by 0.3 nm/K, so that differences in theoperating temperature between different active regions of up to about 40K, which can result in the lateral direction, can significantlyinfluence the width of the emission spectrum of the laser diode chip.

The invention allows for this peak wavelength shift, which is dependenton the operating temperature gradient, to be counteracted by a suitablearrangement and/or configuration of the active regions of the laserdiode chip 2 and/or suitable matching of the laser diode chip and of themount to one another.

FIG. 2 shows an exemplary embodiment of a laser arrangement 1, based ona schematic plan view in FIG. 2A and a schematic section view in FIG.2B. The laser arrangement 1 essentially corresponds to the laserarrangement illustrated in FIGS. 1A and 1B.

In contrast to this, elements of the laser arrangement are matched toone another in such a way that the operating temperature distribution inthe lateral direction in the active regions is homogenized. The activeregions are preferably of the same operating temperatures T_(a), T_(b),T_(c), T_(d), . . . , T_(n) at corresponding points in the respectiveactive region in the lateral direction. In contrast to the laserarrangement shown in FIGS. 1A and 1B, the substrate 3 ends flush withthe mount 6 in the lateral direction in the exemplary embodiment shownin FIG. 2. The edge surface 7 of the mount and the side surface 9 of thesubstrate, as well as the edge surface 8 and the side surface 10, forthis purpose end flush with one another and preferably each form acontinuous surface, particularly preferably a planar surface. Both thesubstrate 3 and the mount 6 limit the laser arrangement 1 in the lateraldirection. Furthermore, the active regions 4 a and 4 n as well as thesemiconductor bodies 5 a and 5 n respectively adjoin the respective sidesurface 10 or 9. The semiconductor bodies 5 n and 5 a, respectively,which are arranged next to the side surfaces 9 and 10 may, inparticular, end flush with the substrate 3.

Lateral widening of the heat flow in the region of the side surfaces 9,10 and of the edge surfaces 7, 8 can thus be avoided. The operatingtemperature stabilization in the lateral direction is in consequencesimplified, since the operating temperature of those active regionswhich are arranged at the edge is matched to that of the active regionswhich are further away from the side surfaces, because the widening ofthe heat flow is suppressed. This is illustrated by the heat flow lines14 and 15 which, in contrast to the lines in FIG. 1, are essentiallystraight lines and run in the vertical direction from the active regioninto the mount.

If required, the active regions 4 a and 4 n which are closest to therespective side surfaces 10 or 9 may also be arranged at a distance fromthese side surfaces in the lateral direction. As a precaution againstsignificant widening of the heat flow in the substrate 3, this distanceis preferably shorter than that between two adjacent active regions ofthe laser diode chip. Furthermore, the distance to the side surface inthe lateral direction is preferably shorter than the distance of thatactive region which is closest to the respective side surface from theactive region adjacent to it (for example shorter than the distancebetween the regions 4 a and 4 b). The distance between that activeregion which is closest to the respective side surface and this sidesurface is particularly preferably shorter than the shortest of thedistances between the active regions of the laser diode chip.Alternatively or additionally, the distances between the active regionsor the lateral dimensions of the active regions can be varied in orderto stabilize the operating temperature (see the description of thefollowing exemplary embodiments).

Furthermore, the side surfaces 9 and 10 may be arranged at a distancefrom the respective edge surfaces 7 and 8 in the lateral direction. As aprecaution against significant widening of the heat flow in the mount 6,this distance is preferably shorter than one of the distances betweentwo adjacent active regions of the laser diode chip and/or is shorterthan the distance between that active region which is closest to therespective side surface and this side surface.

In the case of active regions arranged at equal distances of 110 μm fromone another and with the same lateral dimension, it was possible to keepthe operating temperature at corresponding points in different activeregions essentially constant by such matching of the laser diode chipand the mount, while, in the case of a laser arrangement having areference laser diode chip similar to that shown in FIG. 1, theoperating temperature fluctuated by about 38 K. If the distance betweenthe semiconductor bodies was 200 μm, the fluctuation in the operatingtemperature in the reference laser diode chip was approximately 33 K.This fluctuation could also be compensated.

It was also possible to achieve corresponding compensation of thefluctuation in the operating temperature by matching the laser diodechip 2 to the size of the mount in the case of a laser arrangement asshown in FIGS. 1C and 1D, as well as 1E. The edge-region contacts 50 aand 50 n are in this case preferably arranged in a corresponding mannerto the semiconductor bodies 5 a and 5 n in the lateral direction, asclose as possible to the side surfaces 9, 10 of the substrate 3, and inparticular at the edge of the semiconductor layer structure 500. Inconsequence, the active regions at the edge are advantageously formed asclose as possible to the mount edge or to the substrate edge. Thistherefore provides a particularly efficient precaution against wideningof the heat flow.

FIG. 3A shows one exemplary embodiment of a laser diode chip 2, on thebasis of a schematic plan view.

The laser diode chip 2 corresponds essentially to the laser diode chipdescribed in conjunction with FIGS. 1A and 1B. In contrast to this, thesemiconductor bodies 5 a . . . 5 l with the active regions are notarranged at equal distances along the lateral main extent direction R.The distances D_(ab), D_(bc), D_(cd), D_(de), D_(ef) and D_(fg),respectively, between two adjacent semiconductor bodies in fact increaseas the distance between the semiconductor bodies and the respective sidesurface 10 or 9 of the substrate 3 increases (D_(ab)<D_(bc)<D_(cd)). Thelinear population density of the laser diode chip 2 with active regionsaccordingly decreases in the lateral direction as the distance from therespective side surface increases.

In this case, the expression linear population density means the ratioof the sections occupied by active regions when passing along the laserdiode chip in the lateral direction of main extent R of the laser diodechip to the total distance covered along the lateral main extentdirection of the laser diode chip.

This therefore results in an increase in the loss heat generated in theregion of the side surfaces 9 and 10, such as compared to the laserdiode chips shown in FIG. 1. This makes it possible to compensate forthe lateral widening of the heat flow which occurs as a result of theactive regions being arranged at a distance from the side surface, andto homogenize the lateral operating temperature distribution of theactive regions. The active regions or the semiconductor bodies arepreferably arranged in such a manner that the operating temperatures arethe same (T_(a)=T_(b)= . . . =T_(l)).

For homogeneous distribution of the operating temperature in the lateraldirection, it is particularly advantageous to arrange the active regionsor the semiconductor bodies on the substrate 3 axially symmetricallywith respect to the axis of symmetry 16 of the laser diode chip 2, whichruns perpendicularly to the lateral direction of main extent R and/orparallel to that surface of the substrate 3 on which the semiconductorbodies are arranged. The semiconductor bodies or the active regions arethus preferably arranged symmetrically with respect to this axis ofsymmetry 16. It is particularly preferable for the entire laser diodechip 2 to be designed to be axially symmetrical with respect to thisaxis.

Overall, an operating temperature profile which runs in the same waylaterally in the active regions can thus be achieved by means of asuitable choice of the distances between the adjacent active regions andsemiconductor bodies, in particular in the case of semiconductor bodiesof the same width, as well.

It has been found to be particularly expedient to vary the distancebetween adjacent active regions, particularly in steps of apredetermined size, between a smallest of the distances between adjacentactive regions of D/3, preferably of D/5, particularly preferably ofD/10, and a greatest of the distances between adjacent active regions D.

In the central region around the center of the laser diode chip 2,fluctuations in the operating temperature distribution between differentactive regions, particularly in the lateral direction, are quite small,so that, in some circumstances, there is no need to vary the distancesin order to homogenize the operating temperature distribution in thisregion (D_(de)=D_(ef)=D_(fg) or preferably D_(de)<D_(ef)<D_(fg)).

Corresponding homogenization of the operating temperatures of the activeregions can also be achieved in the case of a laser diode chip 2 whoseactive regions are formed by zones of a continuous active layer 400 intowhich layer current is discretely impressed to form the active regions(see FIGS. 1C, 1D and 1E, respectively). The distances between contacts50 a . . . 50 l are varied in an appropriate manner, instead of varyingthe distances between semiconductor bodies, for this purpose. Thestatements relating to the variation of distances that have been madeabove also apply in a corresponding manner to the exemplary embodimentof a laser diode chip 2 illustrated on the basis of a schematic planview in FIG. 3B. The statements for the semiconductor bodies and theactive regions thus also apply for the configuration of the contacts.

The contacts are preferably formed striplike, in particular in the formof rectangles, when seen in a plan view. In particular, the contacts mayhave the same widths.

A variation of the distance between the adjacent active regions in thisway not only makes it possible to compensate for the operatingtemperature gradient over different active regions of a reference laserdiode chip, but even to reverse this gradient.

This is illustrated in FIGS. 4A and 4B, which each show a schematicsection view through a laser arrangement 1, similar to the laserarrangements shown in FIGS. 1A, 1B and 2. The semiconductor bodies 5 a .. . 5 g and the active regions of the laser diode chips each have thesame widths.

Owing to the widening of the heat flow from the semiconductor bodies 5 a. . . 5 g, which are arranged at equal distances from one another in thereference laser diode chip shown in FIG. 4A, to the side of the sidesurface 9, the operating temperature of the active regions increases inthe lateral direction, starting from this side surface. In the case ofthe laser diode chip shown in FIG. 4B, the distance between adjacentactive regions on the part of the side surface 9 is decreased ascompared to the reference laser diode chip, and is increased on the partof the side surface 10. An increase such as this in the linearpopulation density of the laser diode chip 2 with active regions incomparison to that of the reference laser diode chip shown in FIG. 4A tothe side of the side surface 9 of the substrate 3 makes it possible toreverse the operating temperature gradient, in comparison to that of thereference laser diode chip, despite lateral widening of the heat flow tothe side surface 9 within the substrate. In FIG. 4B, the linearpopulation density decreases in the lateral direction R, starting fromthat active region which is closest to the side surface 9, as thedistance from the side surface 9 increases.

A corresponding situation applies to the influence on the operatingtemperatures for a laser arrangement 1 as shown in FIGS. 1C, 1D, 1E andthe chip as shown in FIG. 3B, for the variation of the distances betweenthe contacts.

In the case of the laser diode chips 2 described in conjunction withFIGS. 1, 2 and 3, the active regions preferably each have the sameactive area.

FIGS. 5A-5B show one exemplary embodiment of a laser diode chip 2according to the invention, based on a schematic plan view. The laserdiode chip 2 essentially corresponds to the laser diode chip describedin conjunction with FIGS. 3A-3B. Instead of or in addition to thevariation of the distances between the semiconductor bodies 5 a . . . 5k or between the active regions, their lateral dimensions, that is tosay the widths b_(a) . . . b_(k) of the semiconductor bodies or of theactive regions are varied.

The active regions accordingly have different widths but, if required,may be arranged at equal distances from one another. The linearpopulation density of the laser diode chip with active regions in zonesof the laser diode chip with pronounced lateral widening of the heatflow can also be increased by variation of the widths, in such a mannerthat the operating temperatures of the active regions are essentiallyconstant (T_(a)= . . . =T_(k)).

The widths of the active regions preferably decrease as the distancefrom the side surface 10 of the substrate 3 increases(b_(a)>b_(b)>b_(c)>b_(d)). In this case as well, and corresponding tothe exemplary embodiment shown in FIGS. 3A-3B, active regions which arearranged comparatively centrally on the substrate 3 may be designed tohave the same widths (b_(d)=b_(e)), because of the comparatively lowinfluence of the widening of the heat flow on the operating temperaturein this zone. Once again, an axially symmetrical arrangement withrespect to the axis of symmetry 16 is particularly suitable for ahomogeneous, in particular symmetrical, operating temperature profile.

It has been found to be particularly expedient for the greatest of thewidths of the active regions of the laser diode chip to be 1.2-times ormore, preferably 1.5-times or more, and particularly preferably twice ormore, than the smallest of the widths of the active regions of the laserdiode chip in the lateral direction of main extent.

The laser diode chip 2, a schematic plan view of which is illustrated inFIG. 5B, corresponds except for the configuration of the contacts to thelaser diode chips described in conjunction with FIGS. 1C and 1D, as wellas 1E. In the case of this chip as well, the operating temperaturedistribution is stabilized, but with the width of the contacts 50 a . .. 50 k having been appropriately varied, in contrast to thesemiconductor bodies as shown in FIG. 5A. The statements relating to thesemiconductor bodies can thus also apply to the contact strips, inparticular to their width.

The active regions shown in FIGS. 5A, 5B have different active areas.

The exemplary embodiments shown in FIGS. 3A, 3B, 4B, 5A and 5B, in whichthe operating temperature distribution is influenced by theconfiguration and/or arrangement of the active regions, may beimplemented in a simpler manner than in the case of the exemplaryembodiment shown in FIG. 2A, owing to the reduced adjustment andmatching effort. However, in the case of the first-mentioned exemplaryembodiments, it may be necessary to adapt the production process for thelaser diode chip, and not to use a standardized process. For example, itmay be necessary to match masks which are used for the formation of thesemiconductor bodies and their contacts to the different dimensions ofand/or distances between the semiconductor bodies and the contacts. Suchmeasures can be dispensed with when the laser diode chip is beingmatched to the mount, for example as in the case of the exemplaryembodiment shown in FIG. 2A.

If required, it is also possible within the scope of the invention touse a suitable deliberate arrangement and/or configuration of the activeregions to also form a predetermined operating temperature profile overthe active regions which has an inhomogeneous profile, that is to saythe operating temperatures can be designed such that they deliberatelydiffer from one another in different active regions, in particular inthe lateral direction.

FIG. 6 shows a schematic plan view of one exemplary embodiment of anoptically pumped semiconductor laser according to an embodiment of theinvention.

The optically pumped semiconductor laser 17 comprises a surface-emittingsemiconductor structure 18 which is optically pumped by means of a laserdiode chip 2 or a laser arrangement 1 as the pump radiation source,which may be designed according to one of the preceding exemplaryembodiments. For this purpose, the pump radiation source is arranged insuch a manner that pump radiation 19 is absorbed in an active zone 20 ofthe semiconductor laser, for example comprising a quantum wellstructure. The active zone is thus optically excited to emit radiationof a wavelength greater than the one of the pump radiation. Thisradiation emerges from a surface of the semiconductor structure. It isthus possible for a radiation field 22 to be formed in an externalresonator of the semiconductor laser 17 which is bounded by means of atleast one external mirror 21. This radiation can be amplified in thesemiconductor structure 18. The resonator is bounded by a further mirror23 which is preferably monolithically integrated, for example as a Braggmirror, in the semiconductor structure 18, in particular together withthe active zone 20. The external mirror 21 is preferably implemented asan output mirror for laser radiation 24 from the resonator. Thesemiconductor laser is, in particular, implemented as an opticallypumped VECSEL.

Since the emission spectrum of the pump radiation source according tothe above embodiments may have a comparatively narrow bandwidth as aresult of the stabilization of the operating temperature and theconfiguration and/or arrangement of the active regions, thesemiconductor laser 17 can be pumped very efficiently and in asimplified manner by means of a pump radiation source whose operatingtemperature has been stabilized.

FIG. 7 shows a schematic plan view of one exemplary embodiment of anoptically pumped laser. As described in conjunction with FIG. 6, a laserdiode chip 2 or a laser arrangement 1 is used as a pump radiationsource, particularly with its operating temperature being stabilized.The pump radiation 19 is absorbed and re-emitted in an amplificationmedium 25 which is suitable for achieving laser activity. The re-emittedradiation is amplified by means of the amplification medium 25 in aresonator, formed by means of the mirrors 26 and 27. The amplifiedradiation can be output from the resonator as laser radiation 24. Thelaser 28 shown in FIG. 7 is, for example, in the form of a solid-statedisk laser, a solid-state rod laser or a fiber laser. Because of thegenerally narrow absorption spectrum in the amplification medium 25,pumping using a pump radiation source which (like the laser arrangementwhose operating temperature has been stabilized, or a correspondinglystabilized laser diode chip) has a narrow emission spectrum isparticularly advantageous.

Furthermore, in the case of a laser diode apparatus having discretelaser diode chips which are arranged on a common chip mount,corresponding operating temperature stabilization can also be achievedby matching the dimensions of the laser diode apparatus to a thermallyconductive mount, variation of the lateral dimensions and/or variationof the distances between the laser diode chips. In the case of laserdiode chips which have a plurality of active regions, operatingtemperature stabilization is, however, particularly advantageous,because of the particularly compact configuration.

Furthermore, within the scope of the invention, a laser arrangement mayalso have a plurality of laser diode chips, whose operating temperatureshave preferably been stabilized.

It should be noted that the invention may also be used, if required, forother radiation-emitting semiconductor chips, such as LED chips having aplurality of active regions arranged in particular on a commonsubstrate. Because the power losses in semiconductor lasers are oftenparticularly high, the invention is, however, particularly suitable forlasers.

The scope of protection of the invention is not limited to the examplesgiven hereinabove. The invention is embodied in each novelcharacteristic and each combination of characteristics, whichparticularly includes every combination of any features which are statedin the claims, even if this feature or this combination of features isnot explicitly stated in the claims or in the examples.

1. A laser arrangement having at least one laser diode apparatus whichhas a side surface which laterally limits the laser diode apparatus, andhas a plurality of active regions which are arranged laterally side byside and are suitable for radiation production, with the laser diodeapparatus being arranged on a mount; and the distance between the sidesurface and an edge which laterally limits the mount on the part of theside surface being shorter than the distance between the active regionclosest to the side surface and the side surface, and/or the distancebetween the side surface and the edge being shorter than one of thedistances between two adjacent active regions of the laser diodeapparatus.
 2. The laser arrangement as claimed in claim 1, wherein thedistance between the side surface and the edge is shorter than theshortest of the distances between the active regions of the laser diodeapparatus.
 3. The laser arrangement as claimed in claim 1, wherein theside surface ends flush with the edge.
 4. The laser arrangement asclaimed in claim 1, wherein the mount is implemented as a heat sink or asubmount.
 5. The laser arrangement as claimed in claim 1, wherein thelaser diode apparatus is a laser diode apparatus having a plurality ofactive regions which are arranged laterally side by side and aresuitable for radiation production, with a lateral dimension of theactive regions being varied in the lateral direction, and/or thedistance between adjacent active regions being varied in the lateraldirection.
 6. A method for stabilizing operating temperaturedistribution of a laser diode apparatus having a plurality of activeregions arranged laterally side by side and configured to generateradiation, the method comprising: providing a reference laser diodeapparatus; measuring an operating temperature distribution of thereference laser diode apparatus; and providing a laser diode apparatuswhose operating temperature is stabilized by at least one of: (a)designing active regions of the laser diode apparatus whose separationis less than a separation of active regions of the reference laser diodeapparatus in zones where the active regions of the reference laser diodeapparatus have a comparatively low operating temperature; and (b)designing active regions of the laser diode apparatus to have lateraldimensions greater than the active regions of the reference laser diodeapparatus in zones where the active regions of the reference laser diodeapparatus have a comparatively low operating temperature.